1. Technical Field of the Invention
The present invention relates to a submarine wellhead, and, more specifically, to a wellhead designed for use on an producing well in a low pressure oil field.
2. Description of the Prior Art
When an submarine oil field goes into production, several wells, spaced out over the surface of the oil field, are connected to a central production platform by means of pipes laid on the ocean floor. Each well is equipped with a wellhead which ensures the water-tightness of the well and has one or more safety valves.
In some oil fields, oil pressure on the wellhead is low and may even be lower than the pressure on the ocean floor, In order to place into production a field of this type, in which the oil does not flow naturally, a pump must be installed, for example at the bottom of the production column.
The traditional method generally uses a centrifugal electric pump, which requires laying an electrical cable between a source, usually mounted on the central platform, and the pump motor. Since it is used in a corrosive environment, the pump has a life of about one year. When the pump breaks down, it is necessary to disconnect the wellhead, pull up the production column holding the pump, replace the pump and then reinstall the production column and the wellhead. This complex and therefore costly operation is further complicated by the need to reestablish the electrical connection to ensure hydraulic flow between the production column and the production line at the wellhead outlet port.